Cisco CCNA (640-553) Security Training – Using the Access-List Dynamic-Extend Command

 In today’s article, I’m going to quickly inform you about the Cisco IOS Global configuration command named “access-list dynamic-extend“.  

Network administrators (like you) use the “access-list dynamic-extend” to allow the absolute timer of the dynamic access control list (ACL) to be extended an additional six minutes.  

In other words, after you’ve enabled the lock-and-key function by using the access-enablecommand and attempt to create a Telnet session to the router to re-authenticate yourself; you can use “access-list dynamic-extend” command to extend the absolute timer of the dynamic ACL by six minutes.  

Note: If you need to use the command, make sure you implement it before the ACL expires. 

Below is the command’s syntax:  

access-list dynamic-extend 

As you can see, the command is really easy to use; it doesn’t have any keywords or arguments.

And, here’s an example of the command being typed on a router.  

Router>enable  

Router#configure terminal  

Router(config)#access-list dynamic-extend  

Router(config)#exit  

Router#copy run start

In the example above, the router is being configured with the command. And, like with mostly all Cisco IOS commands, you can use the word “no” in front of the command to remove (disable) the configured command; like you see below: 

Router(config)#no access-list dynamic-extend 

By the way, if you decide to use the command, make sure your router(s) is running Cisco IOS 12.1(5)T or higher.  

I hope this article was very informative and helped you quickly understand the usage of the access-list dynamic-extend command.